move to sidebar hide Navigation Main page Contents Current events Random article About Wikipedia Contact us Contribute Help Learn to edit Community portal Recent changes Upload file Special pages Search Search Appearance Donate Create account Log in Personal tools Donate Create account Log in Contents move to sidebar hide (Top) 1 History 2 Failover 3 Failback 4 Usage 5 See also 6 References Toggle the table of contents Failover 14 languages العربية বাংলা Čeština Dansk Deutsch Español Français Magyar Italiano 日本語 한국어 Português Русский 中文 Edit links Article Talk English Read Edit View history Tools Tools move to sidebar hide Actions Read Edit View history General What links here Related changes Upload file Permanent link Page information Cite this page Get shortened URL Print/export Download as PDF Printable version In other projects Wikidata item Appearance move to sidebar hide From Wikipedia, the free encyclopedia Automatic switching from failed computer system to standby computers A mobile broadband modem provides a failover Internet connection for network resiliency. Failover is switching to a redundant or standby computer server , system , hardware component or network upon the failure or abnormal termination of the previously active application , [ 1 ] server, system, hardware component, or network in a computer network . Failover and switchover are essentially the same operation, except that failover is automatic and usually operates without warning, while switchover requires human intervention. History [ edit ] The term "failover", although probably in use by engineers much earlier, can be found in a 1962 declassified NASA report. [ 2 ] The term "switchover" can be found in the 1950s [ 3 ] when describing '"Hot" and "Cold" Standby Systems', with the current meaning of immediate switchover to a running system (hot) and delayed switchover to a system that needs starting (cold). A conference proceedings from 1957 describes computer systems with both Emergency Switchover (i.e., failover) and Scheduled Failover (for maintenance). [ 4 ] Failover [ edit ] Systems designers usually provide failover capability in servers, systems or networks requiring high availability and a high degree of reliability . At the server level, failover automation usually sends a heartbeat between two servers, either through the network or through a separate connection (for example, RS-232 ). In the most common design, as long as a regular "pulse" or heartbeat continues between the main server and the second server, the second server will not bring its systems online; however, a few systems actively use all servers and can failover their work to remaining servers after a failure. There may also be a third "spare parts" server that has running spare components for "hot" switching to prevent downtime. The second server takes over the work of the first as soon as it detects an alteration in the heartbeat of the first machine. Some systems have the ability to send a notification of failover. [ citation needed ] Certain systems, intentionally, do not fail over entirely automatically, but require human intervention. This "automated with manual approval" configuration runs automatically once a human has approved the failover. [ citation needed ] Failback [ edit ] Failback is the process of restoring a system, component, or service previously in a state of failure back to its original, working state, and having the standby system go from functioning back to standby. Usage [ edit ] The use of virtualization software has allowed failover practices to become less reliant on physical hardware through the process referred to as migration in which a running virtual machine is moved from one physical host to another, with little or no disruption in service. Failover and failback technology are also regularly used in the Microsoft SQL Server database, in which SQL Server Failover Cluster Instance (FCI) is installed and configured on top of the Windows Server Failover Cluster (WSFC). The SQL Server groups and resources running on WSFC can be manually failed over to the second node [ 5 ] for any planned maintenance on the first node or automatically fail over to the second node in case of any issues on the first node. In the same way, a failback operation can be performed to the first node once the issue is resolved or maintenance is done on it. See also [ edit ] Computer cluster Data integrity Fail-safe Fault-tolerance Fencing (computing) High-availability cluster IT disaster recovery Load balancing Log shipping Safety engineering Teleportation (virtualization) References [ edit ] ^ For application-level failover, see for example Jayaswal, Kailash (2005). "27" . Administering Data Centers: Servers, Storage, And Voice Over IP . Wiley-India. p. 364. ISBN   978-81-265-0688-0 . Retrieved 2009-08-07 . Although it is impossible to prevent some data loss during an application failover, certain steps can [...] minimize it. . ^ NASA Postlaunch Memorandum Report for Mercury-Atlas , June 15, 1962. ^ Petroleum Engineer for Management - Volume 31 - Page D-40 ^ Proceedings of the Western Joint Computer Conference , Macmillan 1957 ^ https://www.dbsection.com/how-to-failover-cluster-from-one-node-to-another/ Retrieved from " https://en.wikipedia.org/w/index.php?title=Failover&oldid=1357654111 " Categories : Computer networking Fault-tolerant computer systems Hidden categories: Articles with short description Short description is different from Wikidata All articles with unsourced statements Articles with unsourced statements from February 2026 This page was last edited on 3 June 2026, at 21:29  (UTC) . Text is available under the Creative Commons Attribution-ShareAlike 4.0 License ; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy . 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